1. The Field of the Invention
The present invention relates to human telomerase, a ribonucleoprotein enzyme involved in human telomere DNA synthesis, and to compounds that inhibit telomerase activity. The invention provides methods, compounds and compositions relating to the fields of molecular biology, chemistry, pharmacology, oncology and medicinal and diagnostic technology.
2. Description of Related Disclosures
The war on cancer has raged for over two decades. Yet, despite the expenditure of over a billion dollars for research and development of new technologies to diagnose and treat malignancies, the age-adjusted cancer mortality rate in the U.S. has remained largely unchanged for the past forty years. Indeed, if current epidemiological trends continue, it appears likely that cancer will overtake cardiovascular disease as the leading cause of death in the United States.
To be sure, some battles have been won and much has been learned about the enemy. A few cancers (e.g., Hodgkin's disease) are now considered curable, and treatment regimes for many other cancers have improved over the last decade. In addition, there has been an explosion of information describing the regulatory mechanisms involved with the onset of malignancy, including the roles of growth factors, receptors, signal transduction pathways, oncogenes, and tumor suppressor genes, in the control of cell growth and differentiation. However, these successes are overshadowed by the fact that cancer is a highly heterogeneous disease in which profound differences exist in the mechanisms by which different cell types become malignant. Thus, although we know more about the mechanisms by which cells become malignant than ever before, each type of cancer presents a unique set of problems in terms of treatment.
Because the cellular mechanisms leading to cancer are so heterogeneous, research on such mechanisms is unlikely to yield a general approach to cancer treatment that is effective and well tolerated by cancer patients. Presently, a variety of non-specific treatment modalities are available, including surgery, radiation, and a variety of cytoreductive and hormone-based drugs, used alone or in combination. Some oncolytic drugs are also available, but the efficacy of these drugs varies among cancer types. Thus, patients suffering from cancer often are forced to undergo treatments that are highly non-specific and highly toxic. Commonly, the toxicity of the treatments produces severe side effects, including nausea and vomiting, hair loss, diarrhea, fatigue, ulcerations and the like, which severely impact the patient's quality of life. In some cases, the impact on the patient's quality of life can be so great that the patient is unable to continue the full course of therapy or opts out of treatment entirely.
Recently, however, an understanding of the mechanisms by which normal cells reach the state of senescence, i.e., the loss of proliferative capacity that cells normally undergo in the cellular aging process, has begun to emerge. The DNA at the ends, or telomeres, of the chromosomes of eukaryotes usually consists of tandemly repeated simple sequences. Scientists have long known that telomeres have an important biological role in maintaining chromosome structure and function. More recently, scientists have speculated that the cumulative loss of telomeric DNA over repeated cell divisions may act as a trigger of cellular senescence and aging, and that the regulation of telomerase, an enzyme involved in the maintenance of telomere length, may have important biological implications. See Harley, 1991, Mutation Research, 256:271-282, incorporated herein by reference.
Telomerase is a ribonucleoprotein enzyme that synthesizes one strand of the telomeric DNA using as a template a sequence contained within the RNA component of the enzyme. See Blackburn, 1992, Annu. Rev. Biochem., 61:113-129, incorporated herein by reference. Methods for detecting telomerase activity, as well as for identifying compounds that regulate or affect telomerase activity, together with methods for therapy and diagnosis of cellular senescence and immortalization by controlling telomere length and telomerase activity, have also been described. See Feng, et al., 1995, Science, 269:1236-1241; Kim, et al., 1994, Science, 266:2011-2014; PCT patent publication No. 93/23572, published Nov. 25, 1993; U.S. patent application Ser. Nos. 08/330,123, filed Oct. 27, 1994; 08/272,102, filed Jul. 7, 1994; 08/255,774, filed Jun. 7, 1994; 08/315,214 and 08/315,216, both of which were filed Sep. 28, 1994; 08/151,477 and 08/153,051, both of which were filed Nov. 12, 1993; 08/060,952, filed May 13, 1993; and 08/038,766, filed Mar. 24, 1993. Each of the foregoing patent applications and references is incorporated herein by reference.
The identification of compounds that inhibit telomerase activity provides important benefits to efforts at treating human disease. Compounds that inhibit telomerase activity can be used to treat cancer, as cancer cells express telomerase activity and normal human somatic cells do not express telomerase activity at biologically relevant levels (i.e., at levels sufficient to maintain telomere length over many cell divisions). Unfortunately, few such compounds have been identified and characterized. Hence, there remains a need for compounds that act as telomerase inhibitors and for compositions and methods for treating cancer and other diseases in which telomerase activity is present abnormally. The present invention meets these and other needs.